The phrase “sleep apnea” generally refers to a condition in which a person, who is initially asleep, stops breathing due to airway blockage, usually as a result of the collapsing of the soft palate. Although sometimes known as “airway occlusion,” the term “apnea” more accurately refers to the actual cessation of breathing. In chronic states, sleep apnea may tend to lead to various physiologic conditions, including, for example, hypoxema, hypercapnia and congestive heart failure. Although the recommended treatment is a tracheostomy, the procedure, unfortunately, may lead to various post-operative complications in the stoma caused by the tracheostomy, leading to a desire for a more efficient and feasible solution.
Although sleep apnea concerns itself with the cessation of breathing, it is important to note that sufferers usually resume breathing within a few seconds, although periods of as long as sixty seconds are not uncommon in serious cases. Sleep apnea is more common amongst people who snore, are obese, consume alcohol or have anatomical abnormalities of the jaw or soft palate. However, atypical cases do occur, and the condition should not be ruled out unilaterally merely because the patient does not fit the profile.
Generally speaking, there are two primary types of sleep apnea, central sleep apnea and obstructive sleep apnea. Central sleep apnea, the rarer of the two, occurs when a problem in the central nervous system (particularly the areas of the brainstem responsible for respiratory drive) interrupts breathing. Overdoses of opiates, including, for example, heroin and morphine, can, in some cases, kill by inducing a severe central sleep apnea (one reason why such drugs are called “respiratory depressants”). Additionally, central sleep apnea is more common at higher elevations.
The Present Invention, however, is concerned more with obstructive sleep apnea, and, therefore, the use of the phrase “sleep apnea” will heretofore be used to mean obstructive sleep apnea. Generally speaking, sleep apnea is caused by the relaxation of the muscles in a person's airway during sleep. While the vast majority of people successfully maintain a patent (i.e., open) upper airway and breathe normally during sleep, a significant number of individuals are prone to severe narrowing (i.e., occlusion) or collapsing of the pharynx or soft palate, such that breathing is impeded or even completely obstructed. As the brain senses a build-up of carbon dioxide, airway muscles are activated which open the airway, allowing breathing to resume, but, in some cases, such as when the muscles cause snoring or a similar reaction, interrupting the person's deep sleep.
It is this recurrent airway obstruction that gives rise to the sleep apnea syndrome, which is also the most common category of sleep-disordered breathing, with 2% of female and 4% of male subjects meeting the minimal diagnostic criteria for sleep apnea of at least 10 apneic events per hour. An “event” can either be an apnea, characterized by the complete cessation of airflow for at least 10 seconds, or a hypopnea, in which airflow decreases by 50 percent for 10 seconds or decreases by 30 percent if there is an associated decrease in the oxygen saturation or an arousal from sleep. To grade the severity of sleep apnea, the number of events per hour is reported as the Apnea-Hypopnea Index. An Index value of less than 5 is considered normal; 5-15 is mild; 15-30 is moderate and more than 30 events per hour characterizes severe sleep apnea.
In addition to the conditions listed above, recurrent episodes of airway obstruction are associated with asphyxia, hypertension, depression and daytime fatigue, since a transient interruption of the sleep cycle accompanies the restoration of airway patency. Most apnetic individuals are not aware of these events, and are usually informed of the symptoms by their sleep partner. The apneic episodes are thought to account for the clinical sequelae (symptoms that arise from a particular condition), which include increased incidence of chronic hypertension, a 700% rise in road traffic accidents, excessive daytime somnolence (similar, but unrelated to narcolepsy), social and family disruption, and cardiac arrhythmias and morbidity. Obstruction of the upper airway may also be a cause of or may contribute to sudden infant death syndrome.
The management of sleep apnea was revolutionized with the introduction of continuous positive airway pressure, in which the airway of the apnetic is forced open through the use of a positive stream of air pressure into the lungs of the apnetic. One such method is described in U.S. Pat. No. 5,950,624 to Hart, the contents of which are hereby incorporated herein in their entirety. Hart discloses a rigid oral appliance for installation within the mouth of an individual to prevent obstruction of the natural airway of the individual and to enhance natural ventilation during sleep. Hart also discloses an embodiment in which the oral appliance may be used without an external positive air supply.
However, Hart is deficient in a number of aspects that ultimately prove it disadvantageous to solving the problem of managing sleep apnea. First, Hart describes a mouthpiece member that is rigid in nature and must be molded to the contours and structure of an individual patient. The necessity of requiring dental molds to be taken and a mouthpiece member created by a lab and fitted to the wearer by a physician greatly reduces the effectiveness of treatment on the general population due primarily to excessive cost. Second, the device disclosed in Hart is, by its design, maximally intrusive. It is intended to fill the entire oral cavity of the wearer. As a result, and as with any foreign object which would be inserted into one's oral cavity during sleep, the natural reaction of the body would be to reject or remove the device. Unfortunately, to the extent that the device is in fact removed during sleep, it is totally ineffective. Thus, a design having a relatively small “footprint” is most preferable, as reducing the intrusiveness of the oral cavity would necessarily result in a more comfortable and acceptable situation, increases the acceptance of the device by the wearer, resulting in a decrease in rejection and an increase of effectiveness. Third, the Hart device does not include a retaining strap, which would preferably serve not only to keep the device in place during use, but also to make the device easy to locate and reinsert if it is removed during sleep. Finally, one of the concerns of intra-oral apnea/snoring devices is that insertion of such devices tends to cause salivation in the wearer. Due to its nature, the device disclosed in Hart doesn't seem to facilitate swallowing, since the whole oral cavity is occupied by the device.
Thus, there exists the need for an oral device, used primarily to prevent sleep apnea but also to prevent snoring and the like, which overcomes the disadvantages listed above.